*author:* **Michał H. Jamróz**, Warsaw

**CHIGRA**

The CHIGRA program for PC computers is based on the hypervertex version of the Chiral Graph Theory restricted to the presence of only asymmetric vertices. The graph is introduced in the form of a HGI (cHiral Graph Index) file specific for CHIGRA which is the Protein Data Base PDB file augmented with additional information about the labels of the chiral atoms and the complex number parameters (a and b) assigned to these very atoms. All C and heteroatoms are set up to be identical vertices while the H-atoms are ignored in the calculations. The program considers complex matrices in the form A+iB and realizes matrix calculations on real matrices preserving the rules of the algebra of complex numbers: (A+iB)(A+iB)=A2-B2+i(BA+AB).

We can apply these rules because all considered matrices, except the chiral incidence matrix, are symmetric. The CHIGRA output contains real and imaginary parts of the Wiener, first and second Zagreb, Laplacian and Randiæ indices.

The HGI CHIGRA input files were generated through the PDB files produced by many molecular graphics programs. The PDB files were edited to obtain the HGI files by introducing the labels of the chiral atoms and the parameters of the complex numbers assigned to them.

M. H. Jamróz, CHIGRA – program calculating chiral graph topological indices for molecules with chiral centres based on the hypervertex Chiral Graph Theory, Institute of Nuclear Chemistry and Technology, Warsaw, 2014. The CHIGRA program is available at the smmg.pl web page.

If CHIGRA not act because of lack of the MSVBVM50.DLL, put MSVBVM50.DLL file into your CHIGRA folder

Program should be cited as:

*Jan Cz. Dobrowolski, M. H. Jamroz, P. F. J. Lipinski, On Chiral Graph Topological Indices of alpha-Amino Acids, MATCH. Commun.Math. Comput. Chem. 76 (2016) 401-418*